[NEW] www/tidy-html5

Tidy is a console application and C library that corrects and cleans
up HTML and XML documents by fixing markup errors and upgrading legacy
code to modern standards. This is the the updated 2015 successor to
the W3C's original html-tidy, now maintained and updated by the HTACG
(HTML Tidy Advocacy Community Group).

This is my first port submission, so any feedback would be
appreciated. I read the OpenBSD Porting Guide and enjoyed learning
about how these tools work, but expect to have made some mistakes. I
hope to be able to learn from them and contribute more over time.